Thursday, 10 November 2011

A New Cambrian Predator To Rival The Mighty Anomalocaris

The Burgess Shale in the Rocky Mountains of Canada is perhaps the most celebrated fossil locality on Earth. The 505 million year old fossils are some of the best preserved ever found. They are weird and wonderful evolutionary marvels incarcerated within the rocks. Primitive trilobites are the most common organisms which can be found at the Burgess Shale. The simple hard-shelled herbivores are similar in shape to a woodlice. Yet where there are herbivores, there will be predators to prey upon them.
The incredible fossils of Tegopelte gigas, first
collected in the 1920s by Charles Doolittle Walcott

The mighty Anomalocaris canadensis a giant, 1 metre long, shrimp-like carnivore, dominated the sea that would become the Burgess Shale. It was the top predator in the ocean for many millions of years. Yet palaeontologists now believe that they have found a formidable contender to it. Tegopelte gigas was first discovered in the 1920s amongst the 40,000 or so fossils collected by Charles Doolittle Walcott, most famous for his excavations at the Burgess Shale.

The two beautifully preserved specimens were consigned to the back rooms of the Smithsonian. Analysis has shown that the creature was one of the larger arthropods of its time, reaching lengths of 30 centimetres, possibly longer. It was rather like a millipede, with 33 pairs of jointed legs and a soft shell covering its body. However not much more was known about it. That situation changed recently. A 2008 excavation at the Burgess Shale has yielded a series of fossils which give us great insight into how this creature moved.

The fossils in question were the tracks from a mysterious creature. The markings, discovered by Jean Bernard Caron, a curator at the Royal Ontario Museum, formed a massive chain. A small piece was taken back for analysis and soon after, air support was sent up to the fossil site. The slab of rock bearing the traces was divided into sections, carefully wrapped up, loaded on to helicopters and flown back to base. A full study was conducted.

They quickly deduced that the tracks were made by Tegopelte. Such an occurrence is rare as it is hard to match a trace fossil to the producer. The long chain of tracks allowed palaeontologists to reconstruct the way the creature moved. They found that it would have been capable of quick scuttles and tight turns, making it very fast and very agile. When they combined this new information with previously known data about Tegopelte, they concluded that it would have been a very efficient and powerful predator.

It was larger than most creatures on Earth at the time, it was soft-shelled which suggests that protecting itself was not high on its evolutionary to-do list, and it was incredibly fast and agile. All or some of these characteristics are found in predators both modern and prehistoric. The Burgess Shale has given palaeontologists an unparalleled view of late Cambrian life. Even today, nearly 100 years since the first excavations by Charles Doolittle Walcott, it is still yielding many surprising and revolutionary finds.